High temperature super-conducting rotor coil support with split coil housing and assembly method

ABSTRACT

A rotor is disclosed for a synchronous machine comprising: a rotor core; a super-conducting coil winding extending around at least a portion of the rotor, said coil winding having a side section adjacent a side of the rotor core; at least one tension rod extending through a conduit in said rotor core; and a housing attached to the tension rod and connected to the side section of the coil winding, wherein the housing comprises a pair of side panels.

RELATED APPLICATIONS

This application is related to the following commonly-owned andcommonly-filed applications (the specifications and drawings of each areincorporated by reference herein):

U.S. patent application Ser. No. 09/854,931 entitled “SynchronousMachine Having Cryogenic Gas Transfer Coupling To Rotor WithSuper-Conducting Coils”, filed May 15, 2001;

U.S. patent application Ser. No. 09/855,026 entitled “High TemperatureSuper-Conducting Synchronous Rotor Coil Support With Tension Rods AndMethod For Assembly Of Coil Support”, filed May 15, 2001;

U.S. patent application Ser. No. 09/854,946 entitled “High TemperatureSuper-Conducting Rotor Coil Support With Tension Rods And Bolts AndAssembly Method”, filed May 15, 2001;

U.S. patent application Ser. No. 09/854,939 entitled “High TemperatureSuper-Conducting Coils Supported By An Iron Core Rotor”, filed May 15,2001;

U.S. patent application Ser. No. 09/854,938 entitled “High TemperatureSuper-Conducting Synchronous Rotor Having An Electromagnetic Shield AndMethod For Assembly”, filed May 15, 2001;

U.S. patent application Ser. No. 09/854,940 entitled “High TemperatureSuper-Conducting Rotor Coil Support And Coil Support Method”, filed May15, 2001;

U.S. patent application Ser. No. 09/854,937 entitled “High TemperatureSuper-Conducting Rotor Having A Vacuum Vessel And Electromagnetic ShieldAnd Method For Assembly”, filed May 15, 2001;

U.S. patent application Ser. No. 09/854,944 entitled “A High PowerDensity Super-Conducting Electric Machine”, filed May 15, 2001;

U.S. patent application Ser. No. 09/854,943 entitled “Cryogenic CoolingSystem For Rotor Having A High Temperature Super-Conducting FieldWinding”, filed May 15, 2001;

U.S. patent application Ser. No. 09/854,464 entitled “High TemperatureSuper-Conducting Racetrack Coil”, filed May 15, 2001; and

U.S. patent application Ser. No. 09/855,034 entitled “High TemperatureSuper Conducting Rotor Power Leads”, filed May 15, 2001.

BACKGROUND OF THE INVENTION

The present invention relates generally to a super-conductive coil in asynchronous rotating machine. More particularly, the present inventionrelates to a coil support structure for super-conducting field windingsin the rotor of a synchronous machine.

Synchronous electrical machines having field coil windings include, butare not limited to, rotary generators, rotary motors, and linear motors.These machines generally comprise a stator and rotor that areelectromagnetically coupled. The rotor may include a multi-pole rotorcore and one or more coil windings mounted on the rotor core. The rotorcores may include a magnetically-permeable solid material, such as aniron-core rotor.

Conventional copper windings are commonly used in the rotors ofsynchronous electrical machines. However, the electrical resistance ofcopper windings (although low by conventional measures) is sufficient tocontribute to substantial heating of the rotor and to diminish the powerefficiency of the machine. Recently, super-conducting (SC) coil windingshave been developed for rotors. SC windings have effectively noresistance and are highly advantageous rotor coil windings.

Iron-core rotors saturate at an air-gap magnetic field strength of about2 Tesla. Known super-conductive rotors employ air-core designs, with noiron in the rotor, to achieve air-gap magnetic fields of 3 Tesla orhigher. These high air-gap magnetic fields yield increased powerdensities of the electrical machine, and result in significant reductionin weight and size of the machine. Air-core super-conductive rotorsrequire large amounts of super-conducting wire. The large amounts of SCwire add to the number of coils required, the complexity of the coilsupports, and the cost of the SC coil windings and rotor.

High temperature SC coil field windings are formed of super-conductingmaterials that are brittle, and must be cooled to a temperature at orbelow a critical temperature, e.g., 27° K, to achieve and maintainsuper-conductivity. The SC windings may be formed of a high temperaturesuper-conducting material, such as a BSCCO(Bi_(x)Sr_(x)Ca_(x)Cu_(x)O_(x)) based conductor.

Super-conducting coils have been cooled by liquid helium. After passingthrough the windings of the rotor, the hot, used helium is returned asroom-temperature gaseous helium. Using liquid helium for cryogeniccooling requires continuous reliquefaction of the returned,room-temperature gaseous helium, and such reliquefaction posessignificant reliability problems and requires significant auxiliarypower.

Prior SC coil cooling techniques include cooling an epoxy-impregnated SCcoil through a solid conduction path from a cryocooler. Alternatively,cooling tubes in the rotor may convey a liquid and/or gaseous cryogen toa SC coil winding that is immersed in the flow of the liquid and/orgaseous cryogen. However, immersion cooling requires the entire fieldwinding and rotor structure to be at cryogenic temperature. As a result,no iron can be used in the rotor magnetic circuit because of the brittlenature of iron at cryogenic temperatures.

What is needed is a super-conducting field winding assemblage for anelectrical machine that does not have the disadvantages of the air-coreand liquid-cooled super-conducting field winding assemblages of, forexample, known super-conductive rotors.

In addition, high temperature super-conducting (HTS) coils are sensitiveto degradation from high bending and tensile strains. These coils mustundergo substantial centrifugal forces that stress and strain the coilwindings. Normal operation of electrical machines involves thousands ofstart-up and shut-down cycles over the course of several years thatresult in low cycle fatigue loading of the rotor. Furthermore, the HTSrotor winding should be capable of withstanding 25% over-speed operationduring rotor balancing procedures at ambient temperature, andnotwithstanding occasional over-speed conditions at cryogenictemperatures during power generation operation. These over-speedconditions substantially increase the centrifugal force loading on thewindings over normal operating conditions.

SC coils used as the HTS rotor field winding of an electrical machineare subjected to stresses and strains during cool-down and normaloperation. They are subjected to centrifugal loading, torquetransmission, and transient fault conditions. To withstand the forces,stresses, strains and cyclical loading, the SC coils should be properlysupported in the rotor by a coil support system. These coil supportsystems hold the SC coil(s) in the HTS rotor and secure the coilsagainst the tremendous centrifugal forces due to the rotation of therotor. Moreover, the coil support system protects the SC coils, andensures that the coils do not prematurely crack, fatigue or otherwisebreak.

Developing support systems for HTS coils has been a difficult challengein adapting SC coils to HTS rotors. Examples of coil support systems forHTS rotors that have previously been proposed are disclosed in U.S. Pat.Nos. 5,548,168; 5,532,663; 5,672,921; 5,777,420; 6,169,353, and6,066,906. However, these coil support systems suffer various problems,such as being expensive, complex and requiring an excessive number ofcomponents. There is a long-felt need for a HTS rotor having a coilsupport system for a SC coil. The need also exists for a coil supportsystem made with low cost and easy-to-fabricate components.

BRIEF SUMMARY OF THE INVENTION

A coil support system has been developed for a racetrack shaped, hightemperature super-conducting (HTS) coil winding for a two-pole rotor ofan electrical machine. The coil support system prevents damage to thecoil winding during rotor operation, supports the coil winding withrespect to centrifugal and other forces, and provides a protectiveshield for the coil winding. The coil support system holds the coilwinding with respect to the rotor. The HTS coil winding and coil supportsystem are at cryogenic temperature while the rotor is at ambienttemperature.

The split-housing coil support is particularly useful for a low powerdensity High Temperature Super-conducting (HTS) electric machine. Thecoil support withstands the high centrifugal and tangential forces thatwould otherwise act on the SC coil. The coil housings are positionedend-to-end along the long side sections of the coil winding in order toevenly distribute the centrifugal and tangential forces that act on thecoil. To reduce the heat leakage, the mass of the coil support has beenminimized to reduce thermal conduction from the rotor through supportinto the cold coil. The coil support is maintained at cryogenictemperatures, as is the field winding.

The coil support system includes a series of coil support assembliesthat span between opposite sides of the racetrack coil winding. Eachcoil support assembly includes a tension rod and a pair of split coilhousings. The tension rods extend between opposite sides of the coilwinding through conduits, e.g., holes, in the rotor core. A split coilhousing at each end of the tension rod attaches to the coil. The housingtransfers centrifugal forces from the coil to the tension rod. Each coilsupport assembly braces the coil winding with respect to the rotor core.The series of coil support assemblies provides a solid and protectivesupport for the coil winding.

Each split coil housing comprises a pair of opposite side panels thatare assembled around the SC coil and grasps an end of the tension rod.The side panels are “C” shape pieces which are fastened together bybolts to enclose the coil between a pair of side panels. Clamping boltshold the side panels together and prevent the coil housing fromsplitting under large centrifugal and tangential loads.

The HTS rotor may be for a synchronous machine originally designed toinclude SC coils. Alternatively, the HTS rotor may replace a copper coilrotor in an existing electrical machine, such as in a conventionalgenerator. The rotor and its SC coils are described here in the contextof a generator, but the HTS coil rotor is also suitable for use in othersynchronous machines.

The coil support system is useful in integrating the coil support systemwith the coil and rotor. In addition, the coil support systemfacilitates easy pre-assembly of the coil support system, coil and rotorcore prior to final rotor assembly. Pre-assembly reduces coil and rotorassembly time, improves coil support quality, and reduces coil assemblyvariations.

In a first embodiment, the invention is a rotor for a synchronousmachine comprising: a rotor core; a super-conducting coil windingextending around at least a portion of the rotor core, the coil windinghaving a side section adjacent a side of the rotor core; at least onetension rod extending through a conduit in the rotor core; and a housingattached to the tension rod and connected to the side section of thecoil winding, wherein the housing comprises a pair of side panels.

In another embodiment, the invention is a method for supporting asuper-conducting coil winding in the rotor core of a synchronous machinecomprising the steps of: extending a tension rod through a conduit inthe rotor core; positioning the coil winding around the rotor core suchthat the tension rod and tension bolt span between side sections of thecoil winding; assembling a pair of side panels of at least one housingaround a side section of the coil winding; securing side panelstogether, and attaching the housing to a first end of the tension rod.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings in conjunction with the text of thisspecification describe an embodiment of the invention.

FIG. 1 is a schematic side elevational view of a synchronous electricalmachine having a super-conductive rotor and a stator.

FIG. 2 is a perspective view of an exemplary racetrack super-conductingcoil winding.

FIG. 3 is a partially cut-away view of the rotor core, coil winding andcoil support system for a high temperature super-conducting (HTS) rotor.

FIGS. 4 and 5 are perspective views of a split coil housing having acoil (FIG. 5) and without a coil (FIG. 4).

FIG. 6 is a perspective view of the rotor core, coil winding and coilsupport system for a high temperature super-conducting (HTS) rotor.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows an exemplary synchronous generator machine 10 having astator 12 and a rotor 14. The rotor includes field winding coils thatfit inside the cylindrical rotor vacuum cavity 16 of the stator. Therotor fits inside the rotor vacuum cavity of the stator. As the rotorturns within the stator, a magnetic field 18 (illustrated by dottedlines) generated by the rotor and rotor coils moves/rotates through thestator and creates an electrical current in the windings of the statorcoils 19. This current is output by the generator as electrical power.

The rotor 14 has a generally longitudinally-extending axis 20 and agenerally solid rotor core 22. The solid core 22 has high magneticpermeability, and is usually made of a ferromagnetic material, such asiron. In a low power density super-conducting machine, the iron core ofthe rotor is used to reduce the magnetomotive force (MMF). The reducedMMF minimizes the amount of super-conducting (SC) coil wire needed forthe coil winding. For example, the solid iron-rotor core may bemagnetically saturated at an air-gap magnetic field strength of about 2Tesla.

The rotor 14 supports at least one longitudinally-extending,racetrack-shaped, high-temperature super-conducting (HTS) coil winding34 (See FIG. 2). The HTS coil winding may be alternatively asaddle-shape or have some other shape that is suitable for a particularHTS rotor design. A coil support system is disclosed here for aracetrack SC coil winding. The coil support system may be adapted forcoil configurations other than a racetrack coil mounted on a solid rotorcore.

The rotor includes a pair of end shafts that bracket the rotor core 22.A collector end shaft 24 has collector rings 78 that provide an externalelectrical coupling for the SC coil. The collector end shaft alsoincludes a cryogen transfer coupling 26 to a source of cryogenic coolingfluid used to cool the SC coil windings in the rotor. The cryogentransfer coupling 26 includes a stationary segment coupled to a sourceof cryogen cooling fluid and a rotating segment which provides coolingfluid to the HTS coil. The opposite end shaft is a drive shaft 30 thatmay be connected to a power turbine. The end shafts are supported bybearings 25 that provide supports for the entire rotor.

FIG. 2 shows an exemplary HTS racetrack field coil winding 34. The SCfield winding coils 34 of the rotor includes a high temperaturesuper-conducting (SC) coil 36. Each SC coil includes a high temperaturesuper-conducting conductor, such as a BSCCO(Bi_(x)Sr_(x)Ca_(x)Cu_(x)O_(x)) conductor wires laminated in a solidepoxy impregnated winding composite. For example, a series of BSCCO 2223wires may be laminated, bonded together and wound into a solid epoxyimpregnated coil.

SC wire is brittle and easy to be damaged. The SC coil is typicallylayer wound SC tape that is epoxy impregnated. The SC tape is wrapped ina precision coil form to attain close dimensional tolerances. The tapeis wound around in a helix to form the racetrack SC coil 36.

The dimensions of the racetrack coil are dependent on the dimensions ofthe rotor core. Generally, each racetrack SC coil encircles the magneticpoles of the rotor core, and is parallel to the rotor axis. The coilwindings are continuous around the racetrack. The SC coils form aresistance-free electrical current path around the rotor core andbetween the magnetic poles of the core. The coil has electrical contacts79 that electrically connect the coil to the collector 78.

Fluid passages 38 for cryogenic cooling fluid are included in the coilwinding 34. These passages may extend around an outside edge of the SCcoil 36. The passageways provide cryogenic cooling fluid to the coil andremove heat from the coil. The cooling fluid maintains the lowtemperatures, e.g., 27° K, in the SC coil winding needed to promotesuper-conducting conditions, including the absence of electricalresistance in the coil. The cooling passages have an input fluid port 39and output fluid port 41 at one end of the rotor core. These fluid (gas)ports 39, 41 connect the cooling passages 38 on the SC coil to tubes inthe rotor end shaft 24 that extend to the cryogen transfer coupling 26.

Each HTS racetrack coil winding 34 has a pair of generally-straight sideportions 40 parallel to a rotor axis 20, and a pair of end portions 54that are perpendicular to the rotor axis. The side portions of the coilare subjected to the greatest centrifugal stresses. Accordingly, theside portions are supported by a coil support system that counteract thecentrifugal forces that act on the coil.

FIG. 3 shows a partially cut-away view of a rotor core 22 and coilsupport system for a high temperature super-conducting (HTS) coilwinding. The coil support systems includes a series of coil supportassemblies spanning through the rotor core and between opposite sides ofthe HTS coil winding. Each coil support assembly comprises a tension rod42 that extends through a conduit 46 of the rotor core, and a split coilhousing 44 that is fastened to the rod and brackets the coil winding.The coil support system provides a structural frame to hold the coilwinding in the rotor.

The principal loading of the HTS coil winding 34 is from centrifugalacceleration during rotor rotation. The coil support assemblies are eachaligned with the centrifugal loading of the coil to provide effectivestructural support to the coil winding under load. To support the sidesections of the coil, each tension rod 42 attaches to the split coilhousings 44. The housings grasp opposite side sections of the coil. Thetension rods 42 extend through a series of conduits 46 in the rotorcore. These rods are aligned with the quadrature axis of the rotor core.

The split coil housings 44 support the coil winding 34 againstcentrifugal forces and tangential torque forces. Centrifugal forcesarise due to the rotation of the rotor. Tangential forces may arise fromacceleration and deceleration of the rotor, and torque transmission.Because the long sides 40 of the coil winding are encased by the splitcoil housings 44 and the flat ends 86 of the tension bolts, the sides ofthe coil winding are fully supported within the rotor.

The conduits 46 are generally cylindrical passages in the rotor corehaving a straight axis. The diameter of the conduits is substantiallyconstant. However, the ends 88 of the conduits may expand to a largerdiameter to accommodate an insulating tube 52. This tube aligns the rod42 in the conduit and provides thermal isolation between the rotor coreand the rod.

At the end of each tension rod, the insulating tube 52 fastens the coilsupport structure to the hot rotor and prevents heat convectiontherebetween. Additionally, there is a lock-nut 84 connected to theinsulating tube 52, that further secures the connection with the tensionrod. The lock-nut 84 and the tube 52 secure the tension rod and splithousing to the rotor core while minimizing the heat transfer from thehot rotor to the housing structure.

The insulator tube 52 is formed of a thermal insulation material. Oneend of the tube may include an external ring (not shown) that abuts thewall of the wide end 88 of the conduit. The other end of the tubeincludes an internal ring (not shown) that engages the lock-nut 84holding the tension rod to the insulating tube. Heat from the rotorwould have to conduct through the length of the insulator tube 52 andthe lock-nut 84 before reaching the tension rod. Thus, the insulatortube thermally isolates the tension rod from the rotor core.

The number of conduits 46 and their location on the rotor core dependson the location of the HTS coils and the number of coil housings neededto support the side sections of the coils. The axes of the conduits 46are generally in a plane defined by the racetrack coil. In addition, theaxes of the conduits are perpendicular to the side sections of the coil.Moreover, the conduits are orthogonal to and intersect the rotor axis,in the embodiment shown here. The number of conduits and the location ofthe conduits will depend on the location of the HTS coils and the numberof coil housings needed to support the side sections of the coils.

There are generally two categories of support for super-conductingwinding: (i) “warm” supports and (ii) “cold” supports. In a warmsupport, the supporting structures are thermally isolated from thecooled SC windings. With warm coil supports, most of the mechanical loadof a super-conducting (SC) coil is supported by structural members thatspan between the cold coils and the warm support members.

In a cold coil support system, the support system is at or near the coldcryogenic temperature of the SC coils. In cold supports, most of themechanical load of a SC coil is supported by the coil support structuralmembers which are at or near cryogenic temperature.

The exemplary coil support system disclosed here is a cold support inthat the tension rods 42, bolts 43 and associated split housings 44 aremaintained at or near a cryogenic temperature. Because the coil supportmembers are cold, these members are thermally isolated, e.g., by thenon-contact conduits through the rotor core, from the rotor core andother “hot” components of the rotor.

The HTS coil winding and structural coil support components are all atcryogenic temperature. In contrast, the rotor core is at an ambient“hot” temperature. The coil supports are potential sources of thermalconduction that would allow heat to reach the HTS coils from the rotorcore. The rotor core becomes hot during operation. As the coil windingsare to be held in super-cooled conditions, heat conduction into thecoils from core is to be avoided.

The coil support system is thermally isolated from the rotor core. Forexample, the tension rods and bolts are not in direct contact with therotor. This lack of contact avoids the conduction of heat from the rotorto the tension rods and coils. In addition, the mass of the coil supportsystem structure has been minimized to reduce the thermal conductionthrough the support assemblies into the coil windings from the rotorcore.

Each tension rod 42 is a shaft with continuity along the longitudinaldirection of the rod and in the plane of the racetrack coil. The tensionrod is typically made of high strength nonmagnetic alloys such asaluminum or an Inconel alloy. The longitudinal continuity of the tensionrods provides lateral stiffness to the coils which provides rotordynamics benefits. Moreover, the lateral stiffness of the tension rods42 permits integrating the coil support with the coils so that the coilcan be assembled with the coil support on the rotor core prior to finalrotor assembly.

The flat surface 86 head of the tension rod supports an inside surfaceof a side of the coil winding. The end 86 of the tension rod may beserrated so that it may be engaged into the annular ridges 134 of anassembly of two coil housing side panels 124 (see FIG. 5). The otherthree surfaces of the side 40 of the coil winding are supported by thesplit housing 44. Each split housing is assembled around the coil andforms a coil casing in cooperation with the bolt head. This casingsupports the coil winding with respect to tangential and centrifugalloads. The casing also allows the coil winding to expand and contractlongitudinally.

FIGS. 4 and 5 (and FIG. 3) show one-half of exemplary “C” shaped sidepanels 124 of the split housing 44. A pair of side panels bracketsopposite sides of a coil 34. Moreover, side panels are arrangedend-to-end along each side of a coil to form a continuous coil supportassembly along a side section 40 of a coil winding 34. An inside surfaceof each side panel has a narrow slot 130 to receive the wedge and an “L”shaped channel 132 to receive a side of the coil. A side surface and aninner surface of the coil rests on orthogonal surfaces of the channel132 of the side panel. An opposite side panel is assembled around thecoil and supports the same inner coil surface and an opposite coil sidesurface.

The outside surface of the coil is supported by a wedge 126 that extendsbetween the side panels on opposite sides of the coil. An individualwedge may be split (as shown in FIGS. 4 and 5) and extend half-wayacross the coil where it abuts with another split wedge. The wedge 126fits into the narrow slot 130 of a side panel. The wedge includes achannel 127 to receive the cooling passage 38 on the outside surface ofthe coil. Further the wedge may include a series of holes 131 that arealigned with holes 133 at the top edge of the side panel. Each pair ofthese holes 131, 133 receive locking pins 136 (FIG. 3) that extendthrough the opposite side panels and wedges to clamp the top edges ofthe side panels and wedges together.

The wedge may be integral to the side panel and extend one-half thewidth of the coil, as shown in FIG. 4. Alternatively, the wedge may be aseparate component that is assembled with the side panel and may extendone half or the entire distance across the width of the coil to anopposite side panel. In addition, the wedge 126 need not be coextensivewith the side panel. The wedge may extend beyond the length of a sidepanel and engage a slot 130 in an adjacent side panel (as shown in FIG.4). Alternatively, the wedge may be coextensive with the side panel, asis shown in FIG. 5.

The side panels 124 have a lower flange 135 on which rests the insidesurface of the coil. Bolt holes 142 in the lower flange allow forclamping bolts to hold together the lower portion of the housing 44. Thelower flange also engages the tension rod 42 or tension bolt 43(depending on whether a solid tension rod is used or a tension rod andbolt assembly is being used).

Each side panel (one-half is shown in FIGS. 4 and 5) has a half section134 of a hole to engage a tension rod or tension bolt. The side panelsshown in FIGS. 4 and 5 have a half section 134 that forms a hole (whenassembled with two pair of side panels) to engage a serrated end of thetension rod 42 (FIG. 5) or the head of a tension bolt 43 (FIG. 4). Thehole formed by the side panel shown in FIG. 4 has a smooth bore and anannular ledge 137 to engage the head of bolt 43. Alternatively, the holeformed by half section 134 of the side panel shown in FIG. 5 is serratedand engages the serrated end of a tension rod. Accordingly, the splithousing 44 may be used with either a tension rod and bolt assembly, or atension rod without a bolt. Further, a lock-nut 138 (see FIG. 6) may beinserted into the threaded hole 134 and the lock-nut may have aninterior hole and ledge to securely hold a tension bolt head 43.

Regardless of the manner in which the tension bolt or tension rod isattached to the lower flange 135 of the side panel, the end of the boltor rod is secured so as to abut the inside surface of the coil. In thisway the end of the tension bolt or rod directly supports the coil.

The split housing may be made of light, high strength material that isductile at cryogenic temperatures. Typical materials for the splithousings are aluminum, titanium, and Inconel alloys. The shape of thesplit housing has been optimized for low weight.

As shown in FIG. 6, a series of split coil housings 44 (and associatedtension bolts 43 and rods 42) may be positioned along the sides 40 ofthe coil winding. The tension bolts 43 screw into threaded holes (notshown) in the end of the tension rod. The depth to which the bolt screwsinto the rod is adjustable. The total length of the tension rod and boltassembly (which assembly spans between the sides of the coil) can bechanged by turning one or both of the bolts into or out of the holes ofthe tension rods. The head of the bolt or the end of the tension rodincludes a flange with a flat outer surface 86. The flange engages therim of the split housing shown in FIG. 4. The flat head 86 of the boltor rod abuts an inside surface of the coil winding 34.

The housings are arranged end-to-end along the length of the sideportion 40 of the coil. The split housings collectively distribute theforces that act on the coil, e.g., centrifugal forces, oversubstantially the entire side sections 40 of the coil. The splithousings 44 prevent the coil side sections 40 from excessive flexing andbending due to centrifugal forces.

The plurality of split housings 44 effectively hold the coil in placewithout affectation by centrifugal forces. Although the split housingsare shown as having a close proximity to one another, the housings needonly be as close as necessary to prevent degradation of the coil causedby high bending and tensile strains during centrifugal loading, torquetransmission, and transient fault conditions.

The coil supports do not restrict the coils from longitudinal thermalexpansion and contraction that occur during normal start/stop operationof the gas turbine. In particular, thermal expansion is primarilydirected along the length of the side sections. Thus, the side sectionsof the coil slide slightly longitudinally with respect to the splithousing and tension rods.

The coil support system of tension rods 42, bolts 43 and split housings44 may be assembled with the HTS coil windings 34 as they are mounted onthe rotor core 22. The tension rods and split housings provide a fairlyrigid structure for supporting the coil winding and holding the longsides of the coil winding in place with respect to the rotor core. Theends of the coil may be supported by split clamps (not shown) at theaxial ends of (but not in contact with) the rotor core 22.

The rotor core and end shafts may be discrete components that areassembled together. The iron rotor core 22 has a generally cylindricalshape 50 suitable for rotation within the rotor cavity 16 of the stator12. To receive the coil winding, the rotor core has recessed surfaces48, such as flat or triangular regions or slots. These surfaces 48 areformed in the curved surface 50 of the cylindrical core and extendinglongitudinally across the rotor core. The coil winding 34 is mounted onthe rotor adjacent the recessed areas 48. The coils generally extendlongitudinally along an outer surface of the recessed area and aroundthe ends of the rotor core. The recessed surfaces 48 of the rotor corereceive the coil winding. The shape of the recessed area conforms to thecoil winding. For example, if the coil winding has a saddle-shape orsome other shape, the recess(es) in the rotor core would be configuredto receive the shape of the winding.

The recessed surfaces 48 receive the coil winding such that the outersurface of the coil winding extends to substantially an envelope definedby the rotation of the rotor. The outer curved surfaces 50 of the rotorcore when rotated define a cylindrical envelope. This rotation envelopeof the rotor has substantially the same diameter as the vacuum rotorcavity 16 (see FIG. 1) in the stator.

The gap between the rotor envelope and stator cavity 16 is arelatively-small clearance, as required for forced flow ventilationcooling of the stator only, since the rotor requires no ventilationcooling. It is desirable to minimize the clearance between the rotor andstator to increase the electromagnetic coupling between the rotor coilwindings and the stator windings. Moreover, the rotor coil winding ispreferably positioned such that it extends to the envelope formed by therotor and, thus, is separated from the stator by only the clearance gapbetween the rotor and stator.

The rotor core, coil windings and coil support assemblies arepre-assembled. Pre-assembly of the coil and coil support reducesproduction cycle, improves coil support quality, and reduces coilassembly variations. Before the rotor core is assembled with the rotorend shafts and other components of the rotor, the tension rods 42 areinserted into each of the conduits 46 that extend through the rotorcore. The insulator tube 52 at each end of each tension rod is placed inthe expanded end 88 at each end of the conduits 46. The tube 52 islocked in place by a retainer locking-nut 84. The bolts 43, if used, maybe inserted before or after the tension rods are inserted into the rotorcore conduits.

When using tension bolts, then a locking nut 138 is placed on each boltand then used to secure the bolt against the split housing. The depth towhich the bolts are screwed into the tension rods is selected such thatthe length from the end of one bolt on a tension rod to the end of theopposite bolt is the distance between the long sides 40 of the coilwinding. When the tension rods and bolts are assembled in the rotor core22, the coil windings 34 are ready to be inserted onto the core.

The coil winding 34 is inserted onto the rotor core such that the flatends 86 of the tension rods 42 or bolts 43 abut the inside surface ofthe side sections 40 of the winding. Once the winding has been insertedover the ends of the rod 42 or bolt 43, the split housings 44 areassembled over the winding. To assemble each housing, the side panelsare placed against opposite sides of the coil, and the wedges are slidinto the narrow slots 130 of the side panels. The lock pin is insertedto hold the wedges and the side panels together. The lock-nut 138 isused to tighten the side panels against the bolt.

The rotor core may be encased in a metallic cylindrical shield 90 (shownby dotted lines) that protects the super-conducting coil winding 34 fromeddy currents and other electrical currents that surround the rotor andprovides a vacuum envelope to maintain a hard vacuum around thecryogenic components of the rotor. The cylindrical shield 90 may beformed of a highly-conductive material, such as a copper alloy oraluminum.

The SC coil winding 34 is maintained in a vacuum. The vacuum may beformed by the shield 90 which may include a stainless steel cylindricallayer that forms a vacuum vessel around the coil and rotor core.

The coil split housings, tension rods and bolts (coil support assembly)may be assembled with the coil winding before the rotor core and coilsare assembled with the collar and other components of the rotor.Accordingly, the rotor core, coil winding and coil support system can beassembled as a unit before assembly of the other components of the rotorand of the synchronous machine.

While the invention has been described in connection with what ispresently considered to be the most practical and preferred embodiment,it is to be understood that the invention is not to be limited to thedisclosed embodiment, but on the contrary, is intended to cover allembodiments within the spirit of the appended claims.

What is claimed is:
 1. In a synchronous machine, a rotor comprising: arotor core having an axis and a conduit extending through the core andperpendicular to the axis, wherein the conduit has openings on oppositesides of the core; a super-conducting coil winding extending around atleast a portion of the rotor, said coil winding having a side sectionadjacent each of the opposite sides of the rotor core; at least onetension rod extending through the conduit in said rotor core, whereinsaid rod extends through the openings on the opposite sides of the coreand opposite ends of the rod are each adjacent a side section of thecoil winding; and a housing attached to each of the opposite ends of thetension rod and connected to the side section of the coil winding,wherein the housing comprises a pair of side panels.
 2. A rotor as inclaim 1 wherein said side panels are on opposite surfaces of the sidesection.
 3. A rotor in claim 1 wherein said housing and tension rod arecooled by conduction from said coil winding.
 4. A rotor as in claim 1wherein said housing further comprises a wedge bridging the side panelsand abutting an outside surface of the coil winding.
 5. A rotor as inclaim 1 wherein the tension rod includes a bolt having a flat surfaceabutting the coil, and having a width commensurate with the sidesection.
 6. A rotor as in claim 1 wherein the tension rod has a serratedend engaging a serrated hole formed by a plurality of side panels.
 7. Arotor as in claim 1 wherein an assembly of two side panels form a holeto engage an end of a tension rod or tension bolt.
 8. A rotor as inclaim 1 wherein the side panel has a pair of orthogonal surfaces thatabut the coil.
 9. A rotor as in claim 1 wherein said housing is formedof a metal material selected from a group consisting of aluminum,Inconel, and titanium alloys.
 10. A rotor as in claim 1 wherein saidtension rod is formed of a non-magnetic metal alloy.
 11. A rotor as inclaim 1 wherein said tension rod is formed of an Inconel alloy.
 12. In asynchronous machine, a rotor comprising: a rotor core having an axis anda conduit extending through the core and perpendicular to the axis,wherein the conduit is has openings on opposite sides of the core; asuper-conducting coil winding extending around at least a portion of therotor, said coil winding having a side section adjacent each of theopposite sides of the rotor core, wherein the coil winding is thermallyisolated from the core; at least one tension rod extending through theconduit in said rotor core, wherein said rod extends through theopenings on the opposite sides of the core and opposite ends of the rodare each adjacent a side section of the coil winding, and wherein therod and conduit are separated by a gap to thermally isolate the rod fromthe core; and a housing attached to each of the opposite ends of thetension rod and connected to the side section of the coil winding,wherein the housing comprises a pair of side panels and wherein thehousing is thermally isolated from the core.
 13. A rotor as in claim 12wherein the coil winding, tension rod, and housing are at cryogenictemperatures.
 14. A rotor as in claim 12 wherein the coil winding,tension rod, and housing are at cryogenic temperatures, and the rotorcore is hot relative to the coil winding.